Fix races around the access to ->s_options

Put generic_show_options read access to s_options under rcu_read_lock,
split save_mount_options() into "we are setting it the first time"
(uses in foo_fill_super()) and "we are relacing and freeing the old one",
synchronize_rcu() before kfree() in the latter.

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

1 files changed, 1 insertions, 2 deletions

diff --git a/fs/affs/super.c b/fs/affs/super.c
index 5ce695e707fe..63f5183f263b 100644
--- a/fs/affs/super.c
+++ b/fs/affs/super.c
@@ -507,8 +507,7 @@ affs_remount(struct super_block *sb, int *flags, char *data)
                 kfree(new_opts);
                 return -EINVAL;
         }
-        kfree(sb->s_options);
-        sb->s_options = new_opts;
+        replace_mount_options(sb, new_opts);
 
         sbi->s_flags = mount_flags;
         sbi->s_mode  = mode;